A recombinant adeno-associated virus vector encoding the leptin gene (rAAV-lep) has been generated (Chen et al., 1996). Central administration of rAAV-lep reduces food intake and body weights in rats. Because this treatment induces long-term changes in energy balance and nutritional state, its effects on reproduction and lactation were studied.

Adult female Sprague-Dawley rats (224±15g, n=19) were used. Rats were injected i.c.v. rAAV-lep (2.2x10¹⁰ particles/10 µl/rat). The controls received green fluorescent protein (rAAV-GFP) gene. After cohabitation with males, 6 (from 10) rAAV-lep treated and 7 (from 9) rAAV-GFP treated rats became pregnant. They were moved into individual cages and their food intake and body weights were measured biweekly. After parturition, pups were kept with dams. Females and their pups were sacrificed 4 weeks after parturition. Serum leptin concentration was determined using a RIA kit (Linco Research). A dot-blot hybridization analysis for measuring uncoupling protein 1 (UCP-1) mRNA expression in brown fat (BAT) was performed (Dhillon et al., 2001). Statistical analyses were Student's t-test or Mann-Whitney U-test.

After rAAV-lep treatment, parturition with normal numbers of pups occurred. Birth weights were smaller in rAAV-lep treated group (table 1). At the age of 4 weeks, pups in rAAV-lep treated group weighed markedly less than the controls (table 1). In dams, hypothalamic leptin transgene expression reduced food intake, body weight and the amount of visceral white adipose tissue (WAT). In line, a reduction in serum level of leptin was found. Increased UCP-1 mRNA in BAT, reflecting increased energy expenditure through non-shivering thermogenesis, persisted in these rats (table 1).
Table 1: Effect of central leptin gene therapy on daily food intake (g), body weight (g), amount of visceral WAT (g), serum leptin level (ng/ml) and UCP-1 mRNA expression in BAT (arbitrary units) in lactating dams and body weights (g) of their pups at birth and the age of 4 weeks.

Mean ± s.e.m. (dams, n=6-7; pups, n=56-73), * p<0.05.

The present results show that leptin gene therapy may influence the growth of the F1 generation, because it weakens maternal energy conservation by suppressing food intake and body adiposity and by increasing energy expenditure through thermogenesis in dams.

Chen, G. et al., PNAS (1996) 93, 14795-14799.
Dhillon, H. et al., Mol. Ther. (2001) 4,139-145.